The present invention is directed to improved catalysts for the copolymerization of epoxides with carbon dioxide.
Epoxides are known to copolymerize with carbon dioxide, with metal containing catalysts such as zinc diethyl and additives, zinc carboxylates, and metal porphyrin complexes.
The resulting copolymers have alternating epoxide and carbon dioxide groups, and are polycarbonates. These copolymers have found uses in many areas, such as ceramic binders, evaporative pattern casting, and adhesives. Epoxides shown to proceed readily in this reaction are ethylene oxide, propylene oxide, cyclohexene oxide, cyclopentene oxide, cis-2-butene oxide, and others.
The catalysts are generally solids which are not soluble in the polymerization solvents. Charging such catalysts to the polymerization reactor requires the handling of solids. Certain of the catalysts are also toxic and noxious to handle. It is therefore desirable to have soluble catalysts which can be charged to the reactor with other feedstocks without special equipment or handling requirements.